Front mech fouling tyre

Mccraque
Mccraque Posts: 819
edited April 2013 in MTB workshop & tech
Switched to a 2.2 Rocket Ron on the rear of my boardman for summer in the week and to my dismay, the front mech fouls the rear tyre when in the small ring on the front.

I had the same model bike last year - with no such issues. The frame was replaced the other week as I cracked it....but to all intents and purposes, the frame and equipment hasn't change.

I've looked at alignment of the mech from above, and straightened it very slightly, but couldn't do it enough to stop the tyre treads growling on the mech as it passed.

I don't think there is much that could be done in terms of the mech height as sits just above the largest ring when in a high gear - so I can't lower it.

Am I missing a trick? Thanks

Comments

  • Chunkers1980
    Chunkers1980 Posts: 8,035
    Pics might help.
  • nicklouse
    nicklouse Posts: 50,675
    get a smaller tyre.

    some frame just dont work with wide tyres.

    I guess you have adjusted the bottom stop?
    and you have checked the wheel for correct dishing.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Mccraque
    Mccraque Posts: 819
    I could get (and actually have resorted to) a smaller tyre Nick - but my point is that I had the same combo last year (albeit on the original rather than replaced frame) - and all worked beautifully.

    2.25 isn't that big!

    The wheel is very slightly out of dish - but that means that it either rubs the tyre a lot of a bit less...depending on the stage of the revolution!
  • cooldad
    cooldad Posts: 32,599
    That's not out of dish, that's buckled.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • Mccraque
    Mccraque Posts: 819
    ok...it's buckled. But the issue remains.
  • The Rookie
    The Rookie Posts: 27,812
    Unless it's out of Dish as well?
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Ouija
    Ouija Posts: 1,386
    As Nicklouse says, adjust the B stop. Chances are the dérailleur is moving closer to the frame than it might need to in order to pull the chain over from the bigger ring. Simply put the chain on the middle ring, screw the B stop screw in and then try jumping down to the little ring. Repeat until you find the point the chain wont jump down and back off the screw a little. Hopefully this will move the dérailleur far enough away from the frame to stop the tyre rubbing against it but not too far that it wont shift down to the smaller ring.

    Also, if it's a newer frame, make sure that the bottom bracket is set up right. If it's not a 73mm shell, the new frame may have the spacers set incorrectly and the rings may be sitting closer to the frame with the dérailleur set up closer.

Categories